1. Field of the Invention
The invention relates to a coaxial conductor structure for fault-free transmission of a TEM basic mode of a RF signal wave.
2. Description of the Prior Art
The transmission quality of coaxial conductors for the TEM basic mode of RF signal waves decreases for increasing signal frequencies, given the fact that undesirable higher-order modes are able to propagate for higher frequencies, for example TE11, TE21 modes etc., which by way of mode conversion processes may be excited at interference locations and then come to overlay the TEM basic mode.
In particular with regard to future expansions of, or changes to, existing transmission ranges to incorporate higher frequencies for RF signals, which have been specified in the frequency usage plan for the Federal German Republic, it is important to look for ways of permitting an essentially fault-free high-frequency signal transmission of the TEM basic mode of RF signals via coaxial lines of a maximum possible diameter, so as to enable maximum possible transmission output for a minimum of losses.
In a contribution by Konoplev, I. V. et al; “Wave Interference and Band Gap Control in Multi-Conductor One-Dimensional Bragg Structures”, Journal of Applied Physics, vol. 97, Nr. 7, p. 073101-073101-7, April 2005, DOI: 10.1063/1, 1863425, a one-dimensional coaxial Bragg structure has been described, which is intended to selectively influence the propagation behavior of electro-magnetic waves by way of constructive and destructive interferences. To this end the coaxial waveguide structure is provided with a periodical structure of groove-like depressions on its inner and outer conductor walls, the geometric design of which impacts in different ways upon the reflection behavior of RF waves which pass through the corrugated coaxial conductor structure.